So here it is.... I finally published the DropBox client library on CodePlex. It is a fully functional Dropbox client library for Windows Phone 7 and it is the same I've used to build BoxFiles. The first version of BoxFiles received a pretty bad review from http://wmpoweruser.com as it was using only the official API that doesn't have any method for generating links to files (the only way to open a file in Windows Phone 7), but after some searching I've found the API and I think that the current version (1.3) is a pretty good app. I will keep my bad review as they asked 50$ to review the application again. In the following weeks I will publish a new version of the Backup/Restore IsolatedStorage project using Dropbox instead of WCF.
I've put a lot of work in this library so if you use it please sustain my work by buying the application and please "try" not to publish a similar app to BoxFiles on the Marketplace.
I've also published the Sqlite and the ZXing projects on CodePlex so you can grab the source code directly from there.
I wish you a Merry Christmas!